Chelford City Regional Wastewater Treatment Plant - Executive Summary

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The Chelford Regional  Wastewater Treatment Plant is a 15.5 MGD plant located in West Harris County, Texas and serves the Mission Bend area.  The plant is near residential and commerical property, and is next to a school. The plant treats domestic sewage and uses chlorine gas to disinfect the treated effluent.  Sulfur dioxide is used to dechlorinate prior to discharge.  There are four one-ton chlorine cylinders and two one-ton sulfur dioxide cylinders in buildings on the plant.  These chemicals are hazardous substances as defined by 40 CFR 68 and 29 CFR 1910.119.  There have been no accidental releases of these chemicals in the last five years. 
The worst case and alternate scenarios utililize the EPA Risk Management Program Guidance for Wastewater Treatment Plants to model the distance to the toxic end point.  The worst case scenario for both chlorine and sulfur dioxide is an urban setting, 1.3 miles to the toxic end point and affecting 23,817 people.  The alternate scenario for chlor 
ine and sulfur dioxide is 0.2 miles to the toxic end point affecting 693 people. 
The process safety hazard analysis was conducted using the what-if methodology.  Sixteen possible release scenarios were analysed using this method.  The consequences of the scenario and ways to prevent or minimize the release of toxic gases are presented.  The safety management plan also contains operating procedures for the chlorine and sulfur dioxide systems.  These procedures deal with handling and storage, controlling leaks, loading and unloading, procedures for changing cylinders, use of SCBA's, first aid and health considerations.  These procedures also include the Standard Operating Procedures (SOP's) for the operator to handle leak detection, alarms and leak notifications. 
To maintain compliance with the OSHA Process Safety Management Standards (PSM), the plant operator will certify that training has been provided to personnel operating the chlorine system and the sulfur dioxide system.  Also, r 
efresher training will be conducted yearly.  This training will cover the areas of process safety information, operating procedures and emergency response procedures.  Training records will be maintained. 
Outside contractors will be given a Contract Information Packet prior to starting work on the plant.  This packet will inform the contractor of the use of toxic chemicals on site and the potential for hazardous releases.  This packet will also inform the contractors of their responsibilities while on site. 
The mechanical integrity section itemizes the preventive maintenance requirements for the chlorine and sulfur dioxide related equipment.  This section also covers training of maintenance personnel.  Inspection and testing procedures for the chlorine and sulfur dioxide equipment are presented here along with the maintenance training documentation. 
The emergency response plan addresses the requirements of 40 CFR 68 pertaining to notification, medical treatment, response procedures, 
planning, use and maintenance of emergency equipment, employee safety training and emergency response evaluation dealing with chlorine and sulfur dioxide gas.  After discovery of a leak, the chief operator and one other person will make an assessment of the situation.  If the assessment indicates that repair is possible, the facility's repair team will be activated.  If the assessment indicates that a major leak has occurred, the local emergency response agency will be notified with a recommendation from the plant operator.  The emergency response plan has been reviewed by the Chelford City MUD and the plant operating company.
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